In the related art, there has been known an approaching-body warning device of such a kind as described below (e.g., see Patent Literature 1). The approaching warning device monitors rear areas on the right and left sides of an automobile with two cameras and displays on separate monitors on the right and left in real time. Then, when it is determined that the own vehicle is in a dangerous situation based on either or both of a distance and a relative speed to an automobile approaching from the rear while monitoring the approaching automobile with a radar sensor arranged on the back of the own vehicle, an image that calls an attention for presence of the approaching automobile is superimposed, for example on the left monitor screen. Further, in Patent Literature 1, it is disclosed that warning sound is produced from a speaker, out of right-left stereo-type speakers, on the side where presence of the automobile approaching from the rear is recognized along with the superimposing.
Further, it has been known a device, for obstacles and automobiles at the front and, in particular, on both sides, that outputs warning information for calling attention to notify presence of danger through right-left lamps and speakers based on target information obtained from reflection waves of radar waves that is radiated thereby (for example, see Patent Document 2).